Access control or security systems for vehicles, and, in particular, work vehicles, have been provided using a variety of techniques and structures. In a security system in common use in automobiles, an electronic module is inserted between the engine control circuit and the engine to disable certain functions of the engine, such as the spark getting to the spark coil. In simple aftermarket security systems such as the above, it is relatively easy to bypass the security system and start the vehicle by inserting one or two simple electrical jumpers between the aftermarket control circuit and the engine. An unauthorized user can easily “hotwire” these work vehicles and automobiles. This is a particular problem in work vehicles that have relatively simply access control systems. In many instances, the work vehicles are not controlled by a microprocessor and thus there are only a few wires and electrical connections in the control circuits that must be established (or bypassed if disabled) to start and run the vehicle.
Many relatively simple work vehicles do have some degree of complexity, in that they also have an electronic circuit that is responsive to operator command signals provided by manually moveable control levers and switches that cause the various fluid actuators on the work vehicle to move. Many work vehicles also have a separate circuit to control the engagement, shifting and disengagement of the transmission. Thus, many work vehicles, such as skid steer loaders and loader-backhoes, have simply engine control circuits and complex microprocessor controller circuits to control the work implements, such as the lifting and tilting of the bucket, the rate of flow of pressurized fluid into and out of the actuators, and similar controller circuits to control transmission operation.
For work vehicles such as the above, and for other vehicles for which an increased level of security is desired, it would be particularly useful to disable not only the engine but also another vehicle function, such as the transmission or the auxiliary fluid control circuit in a work vehicle. The auxiliary fluid control circuit permits the vehicle operator to move the various fluid actuators coupled to the vehicle. As an alternative, the control circuit that controls the transmission could also be disabled. In any vehicle with dual disablement, an unauthorized user, such as a thief, would not only have to bypass or hotwire the security system preventing the engine from starting, but would also be required to independently and separately bypass or hotwire the electronic circuit controlling the auxiliary implements or the transmission (or both). Only by over-coming both the engine and the second system disabling feature could an unauthorized operator start, move, and use the vehicle.
Thus, even if the unauthorized operator could hotwire the engine, his inability to also enable the auxiliary fluid system or the transmission system would make it difficult to operate the vehicle, particularly for example if the various fluid actuators were lowered to engage the ground or the transmission was disabled or in low gear. This additional security feature would make it less likely that a thief would attempt to steal the work vehicle.
It is therefore an object of this invention to provide an access control or security system for a work vehicle having an engine coupled to a transmission and one or more fluid actuated implements. It is a further object of this invention to provide a security system that disables the work vehicle not only by disabling the engine but also by disabling at least one additional system or subsystem of the vehicle, such as the auxiliary fluid actuators or the transmission.